false dawn

From false + dawn, translating Arabic صُبْح كَاذِب‎ (ṣubḥ kāḏib).

false dawn (plural false dawns)

1. A thin ambient light which precedes true dawn, typically by around an hour, in certain parts of the world.
   • 1888, Rudyard Kipling, Plain Tales from the Hills:

     The moon was low down, and there was just the glimmer of the false dawn that comes about an hour before the real one.

2. Something engendering premature hope; a promising sign which in fact leads to nothing.
   • 2010, "It could be a cover-up", The Economist, 10 Jun 2010:

     As Congo nears the 50th anniversary of its independence from Belgium on June 30th, Mr Chebeya’s murky death suggests that 2006 was a false dawn.

• zodiacal light